The present invention relates to engine mounts and, more particularly, to a selectively adjustable mount for intended use with a model airplane engine.
Building scale model airplanes and flying them via remote control has become an increasingly popular hobby in recent years. During this time, modern technological advances have resulted in highly sophisticated, wireless remote control systems for use with such airplanes. As a result of these systems, the hobbyist is now able to fly the airplane at higher speeds and maneuver it remotely with greater accuracy and with less risk of catastrophe than heretofore possible.
Despite these advances, a problem that continues to plague the hobbyist is getting the airplane to simply fly straight ahead when the airfoils (wing flaps, rudders, etc.) are in the nominal or home position. If the axis of rotation of the engine crankshaft is aligned with the centerline of the airplane""s fuselage, the torque introduced into the system by the rotation of the propeller causes the airplane to deviate from a straight flight path, and instead tend to fly in a direction opposite to the direction in which the propellor rotates. Usually, the direction of propeller rotation is clockwise when viewed from the rear of the airplane, which causes the airplane to turn to the left and climb when the axis of rotation and fuselage centerline are coextensive.
To counteract this force, the hobbyist can xe2x80x9ctrimxe2x80x9d the plane, such as by adjusting the position or orientation of one or more of the airfoils controlling the flight path. Trimming is normally done on a xe2x80x9ctrial and errorxe2x80x9d basis, and depends on the speed of the aircraft. Also, level flight at one speed will result in a climb at a higher speed. Consequently, finding the correct adjustment to create a consistently straight flight path via trimming can be not only frustrating to the hobbyist, but also time-consuming. Moreover, trimming does not really solve the problem with any degree of permanency, as changing out the engine would necessitate starting the process all over again. Furthermore, the amount to which the airfoils can be trimmed is finite, and in some extreme cases, the maximum amount of trimming still might not solve the problem.
Instead of trimming the airplane, another option is to physically relocate the engine (which is typically mounted to a xe2x80x9cfirewallxe2x80x9d) so that the axis of rotation of the crankshaft is not aligned with the centerline of the fuselage. Relocating the engine is a laborious process, since it typically involves detaching a separate mount from the firewall and then reattaching it at a new position estimated to correct the problem. As should be appreciated, making even a single change is time-consuming, and can be difficult to accomplish in the field (and in some cases, it may be necessary to reposition the engine several times to achieve the desired result).
Furthermore, if the adjustment is significant, the xe2x80x9cnewxe2x80x9d position of the engine causes the position of the crankshaft to change such that it is no longer in the center of the opening provided in the cowling or cover and may actually interfere with this structure. Making a corresponding adjustment to the position of the cowling or cover is an option, but this is likewise difficult and time-consuming. Having an offset cowling or cover also deleteriously reduces the aesthetic appeal of the airplane (in which most hobbyists take great pride).
In the past, others have proposed adjustable engine mounts for use in model airplanes, but none of which I am aware overcome the foregoing problems. One of the more modem proposals is found in U.S. Pat. No. 5,505,423 to Kusijanovic, the disclosure of which is incorporated herein by reference. Although the mount disclosed in this patent is adjustable in a sense, the range of adjustment permitted is limited. Making the adjustment also requires first loosening a nut on a bolt axially aligned with the crankshaft of the engine, which is difficult to accomplish with the engine in the mounted position. The nature of the mount is also such that an adjustment to the orientation of the axis of rotation of the crankshaft results in a significant positional shift at the tip, which of course is operatively connected to or operatively associated with the propeller. Hence, even if an adjustment is made using this mount to change the orientation of the axis of rotation of the crankshaft it may still be necessary to make a deleterious positional adjustment to the cowling or cover to make sure that the opening in it accommodates the xe2x80x9cnewxe2x80x9d position of the crankshaft.
Accordingly, a need for an improved mount for use with a model airplane engine is identified. Permitting a wide range of adjustment in an easy and efficient manner would be a hallmark of the mount. The mount would also advantageously allow for an adjustment to be made to the orientation of the axis of rotation of the engine crankshaft without the need for a concomitant adjustment to the position of the cowling or cover forming part of the fuselage. The mount would also be simple and inexpensive to manufacture and would be universal in application.
In accordance with a first aspect of the invention, an adjustable mount for intended use with an engine for a model airplane having a fuselage and a firewall is disclosed. The engine rotates a shaft operatively connected to or associated with a propeller about an axis of rotation, and the mount comprises a bracket capable of supporting the engine. The bracket includes a generally convex surface. A base having a first surface adapted for mating with the firewall is coupled to the bracket. The base includes a second, generally concave surface opposite the first surface for mating with the convex surface of the bracket. As a result of this arrangement, the bracket may be moved relative to the base to adjust/change the orientation of the axis of rotation, with a point along or at one end of the shaft remaining at substantially the same position. Consequently, the possible need for a corresponding adjustment to the cowling or cover forming part of the fuselage characteristic of prior art adjustable mounts is eliminated.
In one embodiment, the bracket comprises a body including the generally convex surface and a pair of arms adapted for supporting the engine. Each arm may be substantially L-shaped, and the mount may further include at least one fastener for securing the arm to the body. The bracket includes an opening through which a portion of a first connector extends. The first connector extending through the opening is secured at one end to the base and includes an oversized head at an opposite end.
The mount may further comprise a first wedge part on the first connector. The first wedge part is associated with a structure having at least one dimension that exceeds a corresponding dimension of the opening in the bracket. A second wedge part is also provided on the first connector. The second wedge part has a first side for engaging the first wedge part and a second side generally opposite the first side for engaging the oversized head. A second connector oriented generally transverse to the first connector connects the first and second wedge parts. Upon tightening the second connector, the first and second wedge parts urge the bracket into engagement with the base by wedging action to thus fix the orientation of the axis of rotation.
Preferably, the second connector is elongated in a direction substantially perpendicular to the axis of rotation when the engine is substantially aligned with a centerline of the airplane fuselage. The structure associated with the first wedge part may be a washer having a convex surface for engaging a concave surface of the bracket surrounding the opening. Alternatively, the first wedge part may be provided with a peripheral flange.
In accordance with a second aspect of the invention, an adjustable mount for intended use with an engine for a model airplane having a fuselage and a firewall is disclosed. The engine rotates a shaft operatively connected to or associated with a propeller about an axis of rotation. The mount comprises a bracket for supporting the engine and a base adapted for mounting to the firewall and mating with the bracket. A first connector is operatively connected to or associated with the base, and matching first and second wedge parts are carried on the first connector. A second connector oriented generally transverse to the first connector is provided for connecting the first and second wedge parts. Upon tightening the second connector, the first and second wedge parts urge the bracket into engagement with the base by wedging action to thus fix the orientation of the axis of rotation.
In one embodiment, the bracket includes an opening and at least one dimension of a structure associated with the first wedge part exceeds a corresponding dimension of the opening. Consequently, the first wedge part is captured between the bracket and the second wedge part. The first connector preferably includes an oversized head at one end for capturing the wedge parts. The first connector also passes through a hole in the base and includes a second oversized head at the opposite end. The second connector is elongated in a direction substantially perpendicular to the axis of rotation of the shaft when the engine is substantially aligned with a centerline of the fuselage of the airplane.
The bracket may include a generally convex surface. The base may include a first surface adapted for mating with the firewall and a generally concave surface opposite the first surface for mating with the convex surface of the bracket. As a consequence of this arrangement, the bracket may be moved relative to the base to adjust or change the orientation of the axis of rotation with a position of a point along or at the tip of the shaft remaining substantially the same. The bracket may comprise a body including the generally convex surface and a pair of arms for supporting the engine.
In accordance with a third aspect of the invention, an adjustable mount for intended use with an engine for a model airplane having a firewall and a fuselage is disclosed. The engine rotates a shaft operatively connected to or associated with a propeller about an axis of rotation. The mount comprises means for adjusting or changing the orientation of the orientation of the axis of rotation and means for fixing the orientation of the axis of rotation.
In one embodiment, the adjusting means comprises a bracket for supporting the engine. The bracket includes a generally convex surface. A base coupled to the bracket includes a first surface adapted for mating with the firewall and a second, generally concave surface opposite the first surface for mating with the convex surface of the bracket. The fixing means may comprise a first connector operatively connected to or associated with the base and passing through an opening in the bracket; a first wedge part carried on the first connector; a matching second wedge part carried on the first connector; and a second connector oriented generally transverse to the first connector for connecting the first and second wedge parts. Upon tightening the second connector, the first and second wedge parts urge the bracket into engagement with the base by wedging action to thus fix the orientation of the axis of rotation. One of a washer having a convex surface for engaging a concave surface of the bracket surrounding the opening or a peripheral flange on the first wedge part may be associated with the first wedge part to prevent it from passing through the opening.
In accordance with a fourth aspect of the invention, a method of adjusting the orientation of an axis of rotation of a rotatable shaft in an engine operatively associated with a propeller on a model airplane is disclosed. The method comprises changing the orientation of the axis of rotation with a position of one end of the shaft remaining substantially the same. The method may further comprise fixing the orientation of the axis of rotation using a connector elongated in a direction generally perpendicular to the axis of rotation.